A 59 year old woman presents with several weeks of insomnia and 10 pound weight loss.
TSH <0.02 uiU/ml (Normal 0.50-4.50)
Free T4 5.4 ng/dL (Normal 0.8-1.8)
Below are images of the neck after administration of Iodine-123:
This patient has Graves’ Disease and a cold nodule in the right thyroid lobe.
The diagnosis of Graves’ Disease can be made based on the above images alone, given visualization of the pyramidal lobe and decreased background activity. (Compare the background iodine activity of this case to Endocrinology Case 1). The 24-hour uptake was also increased, measuring 54% (Normal 10-30%).
The patient underwent thyroid ultrasound:
A slightly heterogeneous, isoechoic nodule containing a coarse calcification is noted in the right thyroid gland, measuring up to 3.8 cm.
Subsequent ultrasound-guided fine needle aspiration demonstrated a benign adenomatoid nodule.
Although Iodine-123 imaging is not indicated in the routine evaluation of thyroid nodules, the presence of a cold nodule (with decreased iodine uptake relative to normal thyroid tissue) is associated with a higher risk of malignancy (10-20%) than a nodule with increased uptake (<1%). Ziessman HA, O’Malley JP, Thrall JH, eds. Nuclear Medicine, the Requisites, 4th ed. Philadelphia: Elsevier, 2014.
The prevalence of the thyroid malignancy in Graves’ disease is controversial. Hyperthyroidism was historically thought to be protective for thyroid cancer, and the likelihood of thyroid cancer has been shown to increase with higher serum TSH. Hyamart MR, et al. J Clin Endocrinol Metab 2008;93:809-14. The published rate of malignancy in a thyroid nodule in a patient with Graves’ disease varies widely, from 1%-19%. Cantalamessa L, et al. Arch Intern Med 1999;159:1705-8. Kraimps JL, et al. Br J Surg 2000;87:1111-3. Carnell NE, et al. Thyroid 2009;8:647-52. Patients from areas of endemic iodine deficiency may have a risk at the higher end of this range. Senyurek Giles Y, et al. Surgery 2008;144:1028-36. At this point further evaluation with ultrasound is recommended for a cold nodule on an iodine scan, regardless of thyroid function.
The decision to biopsy a thyroid nodule is based largely on ultrasound imaging features. The most recent American Thyroid Association (ATA) guidelines categorize thyroid nodules into different levels of suspicion based on ultrasound appearance. The recommendation to biopsy is based on nodule size and these sonographic patterns:
